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"Actually, 'rational' encompasses a bit more than that, IMHO. It assumes that faced between putting food on the table and buying a luxury car, one opts to put food on the table ( a simple example, but it should illustrate ). Its not quite the same as the self-interest you describe."

O.K. -- but what if you had to chose between buying groceries today and getting a car that was an absolute requirement for a job, which would put food on the table every day thereafter? A rational decision would take the longer term into account as well as the immediate needs.

A lot of college students have to make a similar decision. They eat macaroni and cheese, take the bus, and live in a dorm for years -- so that they can eventually qualify for a better job. Is that more or less rational than dropping out early to take a job?

A lot of college students have to make a similar decision. They eat macaroni and cheese, take the bus, and live in a dorm for years -- so that they can eventually qualify for a better job. Is that more or less rational than dropping out early to take a job?

In either case, its an act of faith. Faith by definition is not rational.

"O.K. -- but what if you had to chose between buying groceries today and getting a car that was an absolute requirement for a job, which would put food on the table every day thereafter? A rational decision would take the longer term into account as well as the immediate needs.

A lot of college students have to make a similar decision. They eat macaroni and cheese, take the bus, and live in a dorm for years -- so that they can eventually qualify for a better job. Is that more or less rational than dropping out early to take a job?"

True enough. Then we get into opportunity costs. I guess the example I was trying to put forward to kinda missed.

Let me try another: 'Giffen goods'. This is one of the few areas in which rational doesn't appear to apply. Case in point: The increased prices in tennis shoes, and folks still buying them despite the increased price, especially in demographics that would be better served by 3 square meals a day. There are some other areas I could think of examples for.
Typically, the rational person is assumed to have weighed opportunity costs, and forgone the non-utility of such an item in order to provide for their basic needs. I did notice in one of your other posts you touched on this indirectly ( pointing out that there is the generally sound assumption that there aren't too many irrational folks out there with respect to making choices).
Also, kudos for pointing out the difference between positive and normative economics in another post. It is the normative stuff where a lot of fuzziness ( and often mischief ) takes place.